Studies will be done to clarify some of the basic features underlying the diabetes mellitus-like syndrome that can be induced in the sand rat (Psammomys obesus). The factors controlling islet cell secretion of insulin will be sought in isolated islets, and will be compared with other animal species. Extracts of sand rat insulin will be purified, and analyzed for amino acid content. The basis for the high incidence of infections in these animals will be sought, with investigation of the part played by white cells.